Photovoltaic cell, method for manufacturing same, and photovoltaic module

ABSTRACT

A photovoltaic cell is provided, which includes a substrate; a first passivation layer and a first anti-reflection layer disposed on a front surface of the substrate; and a second passivation layer, a PPW layer and at least one silicon nitride layer SiuNv (1&lt;u/v&lt;4) disposed on a rear surface of the substrate. The at least one silicon nitride layer has a refractive index and a thickness in respective ranges of 1.9 to 2.5 and 50 nm to 100 nm. The second passivation layer includes at least one aluminum oxide layer AlxOy (0.8&lt;y/x&lt;1.6), a refractive index and a thickness of which are respectively in ranges of 1.4 to 1.6 and 4 nm to 20 nm. The PPW layer includes at least one silicon oxynitride layer SirOsNt (r&gt;s&gt;t), a refractive index and a thickness of which are respectively in ranges of 1.5 to 1.8 and 1 nm to 30 nm.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 17/386,442, filed on Jul. 27, 2021, which claims the benefit ofpriority to Chinese Patent Application No. 202011591700.4 filed on Dec.29, 2020, each of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

Generally, the present disclosure relates to a photovoltaic field, inparticular to a photovoltaic cell, a method for manufacturing thephotovoltaic cell and a photovoltaic module.

BACKGROUND

A typical passivated emitter and rear cell (PERC) uses stacked aluminumoxide/silicon nitride as a rear passivation layer. An aluminum oxidelayer has a relatively high fixed negative charge density, and a largenumber of the fixed negative charges may shield electrons on a siliconsubstrate surface, thus reducing the electrons usable for recombinationand achieving suppression of carrier recombination on the surface. ThePERC has become a mainstream technology in the photovoltaic cell.However, for a PERC based photovoltaic module, a potential induceddegradation (PID) effect may negatively affect the performance of thecell, thus resulting in lowered conversion efficiency. An importantcause of the PID effect may be that a potential difference between thecells and other structures (such as a packaging material) of thephotovoltaic module disturbs a normal current path in the cells duringthe power generation, then the photovoltaic cell presents undesirablesituations such as power attenuation and lower power generation.Therefore, it is desirable to improve an anti-PID effect of the PERC andmaintain high efficiency of the PERC.

SUMMARY

Some embodiments of the present disclosure provide a photovoltaic cell,a method for manufacturing the photovoltaic cell, and a photovoltaicmodule, which can improve anti-PID performance and power generationefficiency of the photovoltaic cell.

In order to solve the above problems, embodiments of the presentdisclosure provide a photovoltaic cell, including: a substrate; a firstpassivation layer and a first anti-reflection layer that aresequentially disposed on a front surface of the substrate in a directionaway from the substrate; and a second passivation layer, a polarizationphenomenon weakening (PPW) layer and at least one silicon nitride layerSi_(u)N_(v) that are sequentially disposed on a rear surface of thesubstrate in a direction away from the substrate, where 1<u/v<4. In someembodiments, the second passivation layer includes at least one aluminumoxide layer Al_(x)O_(y), where 0.8<y/x<1.6, a refractive index of the atleast one aluminum oxide layer is in a range of 1.4 to 1.6, and athickness of the at least one aluminum oxide layer is in a range of 4 nmto 20 nm. In some embodiments, the PPW layer includes at least onesilicon oxynitride layer Si_(r)O_(s)N_(t), where r>s>t, a refractiveindex of the at least one silicon oxynitride layer is in a range of 1.5to 1.8, and a thickness of the at least one silicon oxynitride layer isin a range of 1 nm to 30 nm. In some embodiments, a refractive index ofthe at least one silicon nitride layer is in a range of 1.9 to 2.5, anda thickness of the at least one silicon nitride layer is in a range of50 nm to 100 nm.

In some embodiments, the at least one silicon nitride layer includes afirst silicon nitride layer, a second silicon nitride layer and a thirdsilicon nitride layer stacked in the direction away from the substrate,wherein a thickness of the first silicon nitride layer is in a range of5 nm to 20 nm, a thickness of the second silicon nitride layer is in arange of 20 nm to 40 nm, and a thickness of the third silicon nitridelayer is in a range of 40 nm to 75 nm.

In some embodiments, refractive indexes of the first silicon nitridelayer, the second silicon nitride layer and the third silicon nitridelayer decrease layer by layer in the direction away from the substrate,a refractive index of the first silicon nitride layer is in a range ofbetween 2.1 to 2.5, a refractive index of the second silicon nitridelayer is in a range of 2 to 2.3, and a refractive index of the thirdsilicon nitride layer is in a range of 1.9 to 2.1.

In some embodiments, a concentration of silicon atoms in the at leastone silicon oxynitride layer is between 5×10²¹/cm³ and 2.5×10²²/cm³.

In some embodiments, the second passivation layer further includes asilicon oxide layer, and the silicon oxide layer is disposed between thesubstrate and the at least one aluminum oxide layer.

In some embodiments, a thickness of the silicon oxide layer is in arange of 0.1 nm to 5 nm.

Embodiments of the present disclosure further provide a method formanufacturing a photovoltaic cell, including: providing a substrate;forming a first passivation layer and a first anti-reflection layersequentially on a front surface of the substrate in a direction awayfrom the substrate; and forming a second passivation layer, apolarization phenomenon weakening (PPW) layer and at least one siliconnitride layer Si_(u)N_(v) sequentially on a rear surface of thesubstrate in a direction away from the substrate, wherein 1<u/v<4;wherein the second passivation layer includes at least one aluminumoxide layer Al_(x)O_(y), wherein 0.8<y/x<1.6 and a refractive index ofthe at least one layer aluminum oxide layer is in a range of 1.4 to 1.6,and a thickness of the at least one aluminum oxide layer is in a rangeof 4 nm to 20 nm; wherein the PPW layer includes at least one siliconoxynitride layer Si_(r)O_(s)N_(t), wherein r>s>t and a refractive indexof the at least one silicon oxynitride layer is in a range of 1.5 to1.8, and a thickness of the at least one silicon oxynitride layer is ina range of 1 nm to 30 nm; wherein a refractive index of the at least onesilicon nitride layer is in a range of 1.9 to 2.5, and a thickness ofthe at least one silicon nitride layer is in a range of 50 nm to 100 nm.

In some embodiments, where forming the second passivation layerincludes: depositing the at least one aluminum oxide layer on the rearsurface of the substrate, wherein precursors of the at least onealuminum oxide layer include argon, trimethylaluminium and nitrousoxide, wherein a gas flow ratio of the argon, the trimethylaluminium andthe nitrous oxide is in a range of 1:1:1 to 1.5:1:2.

In some embodiments, forming the PPW layer includes: depositing the atleast one silicon oxynitride layer on a surface of the at least onealuminum oxide layer, wherein precursors of the at least one siliconoxynitride include silanes, ammonia and nitrous oxide, wherein a gasflow ratio of the silanes, the ammonia and the nitrous oxide is in arange of 1:1:3 to 1:4:6.

In some embodiments, forming the PPW layer includes: depositing anintermediate silicon oxide layer on a surface of the at least onealuminum oxide layer first, wherein precursors of the intermediatesilicon oxide layer include silanes and nitrous oxide, wherein a gasflow ratio of the silanes and the nitrous oxide is in a range of 1:3 to1:6; and introducing nitrogen source gas to produce nitrogen plasmas toreact with the intermediate silicon oxide layer, so as to form the atleast one silicon oxynitride layer.

In some embodiments, forming the at least one silicon nitride layerincludes: depositing the at least one silicon nitride layer on a surfaceof the silicon oxynitride layer, wherein precursors of the at least onesilicon nitride layer include the silanes and ammonia, wherein a gasflow ratio of the silanes and the ammonia is in a range of 1:1.3 to 1:4.

In some embodiments, the at least one silicon nitride layer includesthree silicon nitride layers, and forming the three silicon nitridelayers includes: forming a first silicon nitride layer on the surface ofthe silicon oxynitride layer, wherein precursors of the first siliconnitride layer include the silanes and the ammonia, wherein the gas flowratio of the silanes and the ammonia is in a range of 1:1.3 to 1:1.5;forming a second silicon nitride layer on a surface of the first siliconnitride layer, wherein precursors of the second silicon nitride layerinclude the silanes and the ammonia, wherein the gas flow ratio of thesilanes and the ammonia is in a range of 1:1.5 to 1:2.2; and forming athird silicon nitride layer on a surface of the second silicon nitridelayer, wherein precursors of the third silicon nitride layer include thesilanes and the ammonia, wherein the gas flow ratio of the silanes andthe ammonia is in a range of 1:2.2 to 1:4.

In some embodiments, a thickness of the first silicon nitride layer isin a range of 5 nm to 20 nm, a thickness of the second silicon nitridelayer is in a range of 20 nm to 40 nm, and a thickness of the thirdsilicon nitride layer is in a range of 40 nm to 75 nm.

In some embodiments, a refractive index of the first silicon nitridelayer is in a range of 2.1 to 2.5, a refractive index of the secondsilicon nitride layer is in a range of 2 to 2.3, and a refractive indexof the third silicon nitride layer is in a range of 1.9 to 2.1.

In some embodiments, forming the second passivation layer furtherincludes: forming a silicon oxide layer between the substrate and the atleast one aluminum oxide layer.

In some embodiments, a thickness of the silicon oxide layer is in arange of 0.1 nm to 5 nm.

Embodiments of the present disclosure further provide photovoltaicmodule, including at least one photovoltaic cell string, wherein each ofthe at least one photovoltaic cell string is composed of a plurality ofphotovoltaic cells electrically connected; wherein each of the pluralityof photovoltaic cells includes: a substrate; a first passivation layerand a first anti-reflection layer that are sequentially disposed on afront surface of the substrate in a direction away from the substrate;and a second passivation layer, a polarization phenomenon weakening(PPW) layer and at least one silicon nitride layer Si_(u)N_(v) that aresequentially disposed on a rear surface of the substrate in a directionaway from the substrate, wherein 1<u/v<4; wherein the second passivationlayer includes at least one aluminum oxide layer Al_(x)O_(y), wherein0.8<y/x<1.6 and a refractive index of the at least one aluminum oxidelayer is in a range of 1.4 to 1.6, and a thickness of the at least onealuminum oxide layer is in a range of 4 nm to 20 nm; wherein the PPWlayer includes at least one silicon oxynitride layer Si_(r)O_(s)N_(t),wherein r>s>t and a refractive index of the at least one siliconoxynitride layer is in a range of 1.5 to 1.8, and a thickness of the atleast one silicon oxynitride layer is in a range of 1 nm to 30 nm;wherein a refractive index of the at least one silicon nitride layer isin a range of 1.9 to 2.5, and a thickness of the at least one siliconnitride layer is in a range of 50 nm to 100 nm.

In some embodiments, the at least one silicon nitride layer includes afirst silicon nitride layer, a second silicon nitride layer and a thirdsilicon nitride layer stacked in the direction away from the substrate,wherein a thickness of the first silicon nitride layer is in a range of5 nm to 20 nm, a thickness of the second silicon nitride layer is in arange of 20 nm to 40 nm, and a thickness of the third silicon nitridelayer is in a range of 40 nm to 75 nm.

In some embodiments, refractive indexes of the first silicon nitridelayer, the second silicon nitride layer and the third silicon nitridelayer decrease layer by layer in the direction away from the substrate,a refractive index of the first silicon nitride layer is in a range ofbetween 2.1 to 2.5, a refractive index of the second silicon nitridelayer is in a range of 2 to 2.3, and a refractive index of the thirdsilicon nitride layer is in a range of 1.9 to 2.1.

In some embodiments, a concentration of silicon atoms in the at leastone silicon oxynitride layer is between 5×10²¹/cm³ and 2.5×10²²/cm³.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are described as examples with reference to thecorresponding figures in the accompanying drawings, and the examples donot constitute a limitation to the embodiments. Elements with the samereference numerals in the accompanying drawings represent similarelements. The figures in the accompanying drawings do not constitute aproportion limitation unless otherwise stated.

FIG. 1 is a schematic structural diagram of a photovoltaic cellaccording to some embodiments of the present disclosure;

FIG. 2 is another structural diagram of the photovoltaic cell accordingto some embodiments of the present disclosure;

FIG. 3 is yet another structural schematic diagram of the photovoltaiccell according to some embodiments of the present disclosure;

FIG. 4 is a schematic flow chart of a method for manufacturing aphotovoltaic cell according to some embodiments of the presentdisclosure; and

FIG. 5 is a schematic structural diagram of a photovoltaic cellaccording to a comparative example provided in the present disclosure.

DETAILED DESCRIPTION

The embodiments of the present disclosure will be described in detailbelow with reference to the accompanying drawings in order to make theobjectives, technical solutions and advantages of the present disclosureclearer. However, it will be appreciated by those of ordinary skill inthe art that, in various embodiments of the present disclosure, numeroustechnical details are set forth in order to provide the reader with abetter understanding of the present disclosure. However, the technicalsolutions claimed in the present disclosure may be implemented withoutthese technical details and various changes and modifications based onthe following embodiments.

The present disclosure provides a photovoltaic cell, which includes asubstrate; a first passivation layer and a first anti-reflection layerthat are sequentially disposed on a front surface of the substrate in adirection away from the substrate; and a second passivation layer, apolarization phenomenon weakening (PPW) layer and at least one siliconnitride layer Si_(u)N_(v) that are sequentially disposed on a rearsurface of the substrate in a direction away from the substrate, where1<u/v<4. The second passivation layer includes at least one aluminumoxide layer Al_(x)O_(y), where 0.8<y/x<1.6 and a refractive index of theat least one aluminum oxide layer is in a range of 1.4 to 1.6, and athickness of the at least one aluminum oxide layer is in a range of 4 nmto 20 nm. The PPW layer includes at least one silicon oxynitride layerSi_(r)O_(s)N_(t), where r>s>t and a refractive index of the at least onesilicon oxynitride layer is in a range of 1.5 to 1.8, and a thickness ofthe at least one silicon oxynitride layer is in a range of 1 nm to 30nm. A refractive index of the at least one silicon nitride layer is in arange of 1.9 to 2.5, and a thickness of the at least one silicon nitridelayer is in a range of 50 nm to 100 nm.

By disposing the PPW layer including the at least one silicon oxynitridelayer between the at least one aluminum oxide layer and the at least onesilicon nitride layer, a potential difference between the at least onealuminum oxide layer and the at least one silicon nitride layer may bereduced, and the anti-PID performance of the photovoltaic cell may beimproved, thus ensuring the high conversion efficiency of thephotovoltaic cell. Furthermore, a refractive index of each layer on therear surface of the photovoltaic cell is within a reasonable refractiveindex range by defining a relationship between the atom number of eachkind of atoms in the silicon nitride layer, the aluminum oxide layer andthe silicon oxynitride layer. When the refractive index of all thelayers on the rear surface of the photovoltaic cell is within thereasonable refractive index range and each layer has a suitablethickness, the light utilization rate of the photovoltaic cell can beincreased and the light conversion efficiency of the photovoltaic cellcan be improved.

Some embodiments of the photovoltaic cell of the present disclosure willbe described in detail below. The following contents are merely providedfor convenience of understanding the implementation details, and are notnecessary for the implementation of the technical solution of thepresent disclosure.

FIG. 1 is a schematic structural diagram of a photovoltaic cellaccording to some embodiments of the present disclosure.

As shown in FIG. 1 , the photovoltaic cell includes a substrate 10. Thesubstrate 10 includes an intrinsic silicon substrate 11 and an emitter12. The intrinsic silicon substrate 11 and the emitter 12 form a PNjunction of the photovoltaic cell. For example, the intrinsic siliconsubstrate 11 may be a P-type substrate, the emitter 12 may be an N-typedoped layer, that is, the P-type substrate and the N-type doped layerform a PN junction. In some embodiments, the intrinsic silicon substrate11 includes, but is not limited to, a monocrystalline silicon substrate,a polycrystalline silicon substrate, a monocrystalline silicon-likesubstrate, etc. It should be noted that a front surface of the substrate10 is designated as a light-receiving surface, and a rear surface of thesubstrate 10 refers to a surface opposite to the front surface. In someembodiments, a surface close to the emitter 12 is referred to as thefront surface, and a surface close to the intrinsic silicon substrate 11is referred to as the rear surface.

The photovoltaic cell further includes a first passivation layer 13 anda first anti-reflection layer 14 that are sequentially disposed on thefront surface of the substrate 10 in a direction away from the substrate10. In some embodiments, the photovoltaic cell further includes a firstelectrode 15 penetrating through the first passivation layer 13 and thefirst anti-reflection layer 14 and forming an ohmic contact with theemitter 12 of the substrate 10.

Herein, the first passivation layer 13 includes, but is not limited to,an aluminum oxide layer, a silicon nitride layer, a silicon oxynitridelayer, etc. The first passivation layer 13 is configured to reduce therecombination of carriers, thereby increasing an open circuit voltageand a short circuit current of the photovoltaic cell. The firstanti-reflection layer 14 may be provided with a layer similar to orsubstantially the same as the first passivation layer 13, for example,including but not limited to the aluminum oxide layer, the siliconnitride layer, the silicon oxynitride layer, etc. The firstanti-reflection layer 14 may not only reduce the reflectivity of lightsincident on a surface of the photovoltaic cell, but also passivate thesurface of the photovoltaic cell.

The photovoltaic cell further includes a second passivation layer 20, apolarization phenomenon weakening (PPW) layer 18 and a silicon nitridelayer 19 that are sequentially disposed on the rear surface of thesubstrate 10 in a direction away from the substrate 10. In someembodiments, the photovoltaic cell further includes a second electrode21 penetrating through the second passivation layer 20, the polarizationphenomenon weakening layer 18 and the silicon nitride layer 19 andforming an ohmic contact with the substrate 10.

The second passivation layer 20 includes at least one aluminum oxidelayer Al_(x)O_(y), where 0.8<y/x<1.6. Particularly, 0.8<y/x≤1,1<y/x<1.5, or 1.5≤y/x<1.6. When the at least one aluminum oxide layer isprovided with a single layer (i.e., an aluminum oxide layer 17 shown inFIG. 1 ), a thickness of the aluminum oxide layer 17 is in a range of 4nm to 20 nm. Particularly, the thickness of the aluminum oxide layer 17is 5 nm, 10 nm, 15 nm or 20 nm. When forming the aluminum oxide layer 17with a particular thickness, a ratio of y and x in the aluminum oxidelayer 17 is controlled in a range of 0.8 to 1.6, and a refractive indexof the aluminum oxide layer 17 is in a range of 1.4 to 1.6.Particularly, the refractive index of the aluminum oxide layer 17 is ina range of 1.55 to 1.59. It should be noted that, when the at least onealuminum oxide layer is provided with a plurality of layers (not shown),the refractive index mentioned here should be a refractive index of allthe aluminum oxide layers, that is, the refractive index of all of theplurality of aluminum oxide layers is in a range of 1.4 to 1.6.Particularly, the refractive index of all of the plurality of aluminumoxide layers is in a range of 1.55 to 1.59.

As shown in FIG. 1 , the second passivation layer 20 further includes asilicon oxide layer 16. The silicon oxide layer 16 is disposed betweenthe substrate 10 and the aluminum oxide layer 17 to isolate the aluminumoxide layer 17 from the substrate 10, thereby avoiding a direct contactbetween the aluminum oxide layer 17 and the substrate 10. A densesilicon oxide layer 16 is chemically stable, which may chemicallypassivate a dangling bond on the surface of the substrate 10. Herein, athickness of the silicon oxide layer 16 is in a range of 0.1 nm to 5 nm.Particularly, the thickness of the silicon oxide layer 16 is 2 nm, 3 nmor 4 nm.

It is found through an experimental verification that the PID may beimproved by 21.2% to 27.7% via providing the silicon oxide layer 16 witha special design (for example, the thickness of the silicon oxide layer16 is in a range of 0.1 nm to 5 nm) compared with providing apassivation layer without silicon oxide.

The polarization phenomenon weakening layer 18 includes at least onesilicon oxynitride layer Si_(r)O_(s)N_(t), where r>s>t. A concentrationof silicon atoms in the at least one silicon oxynitride layer is in arange of 5×10²¹/cm³ to 2.5×10²²/cm³. The PPW layer 18 is configured toreduce a cell difference between layers on two sides of the PPW layer18, so as to improve the anti-PID effect. In some embodiments, athickness of the at least one silicon oxynitride layer in the PPW layer18 is in a range of 1 nm to 30 nm. Particularly, the thickness of the atleast one silicon oxynitride layer is 6 nm, 11 nm, 16 nm, 21 nm, 25 nmor 30 nm. When forming the at least one silicon oxynitride layerSi_(r)O_(s)N_(t) with a particular thickness, where r>s>t, a refractiveindex of the at least one silicon oxynitride layer is in a range of 1.5to 1.8. It should be noted that when the at least one silicon oxynitridelayer is provided with a plurality of layers (not shown), the refractiveindex mentioned here should be a refractive index of all the siliconoxynitride layers, that is, the refractive index of all of the pluralityof silicon oxynitride layers is in a range of 1.5 to 1.8.

It is found through an experimental verification that the PID may beimproved by 42.8% to 69.60% via providing the PPW layer 18 with aspecific design (for example, a thickness of the PPW layer is in a rangeof 1 nm to 30 nm) compared with providing a passivation layer withoutthe PPW layer.

It is found through an experimental verification that, in someembodiments, the PID may be improved by up to 81.6% to 99.00% when therear surface of the photovoltaic cell is provided with both the siliconoxide layer 16 and the PPW layer 18 for isolation.

In an embodiment, the at least one silicon nitride layer Si_(u)N_(v) isprovided with a single layer (i.e., the silicon nitride layer 19 shownin FIG. 1 ), where 1<u/v<4. Particularly, 1<u/v≤2 or 2<u/v<4. Athickness of the silicon nitride layer 19 is in a range of 50 nm to 100nm. Particularly, the thickness of the silicon nitride layer 19 is 60nm, 75 nm or 90 nm. When forming the silicon nitride layer 19 with aparticular thickness, the ratio of u and v in the silicon nitride layer19 may be controlled in a range of 1 to 4, and a refractive index of thesilicon nitride layer 19 is in a range of 1.9 to 2.5. In someembodiments, the at least one silicon nitride layer is provided with aplurality of layers (shown in FIG. 2 and FIG. 3 ), for example, 2 to 5layers. Refractive indexes of the plurality of silicon nitride layersdecrease layer by layer in the direction away from the substrate 10, buta refractive index of all the silicon nitride layers should becontrolled in a range of 1.9 to 2.5. It should be noted that the numberof the plurality of silicon nitride layers may be configured accordingto requirements on the thickness and refractive index of the depositedsilicon nitride layer, which is not limited in the present disclosure.

In order to achieve a photovoltaic cell with high anti-PID effect andhigh efficiency, for example, the thicknesses of the second passivationlayer 20, the PPW layer 18 and the silicon nitride layer 19 on the rearsurface of the photovoltaic cell and their corresponding refractiveindexes are designed to be matched. The refractive index of all thelayers on the rear surface of the photovoltaic cell is within areasonable refractive index range by defining a relationship of the atomnumber of each kind of atoms in the aluminum oxide layer 17 included inthe second passivation layer 20, the polarization phenomenon weakeninglayer 18 and the silicon nitride layer 19. When the refractive index ofall the layers on the rear surface of the photovoltaic cell is withinthe reasonable refractive index range and each layer has a suitablethickness, which result in a relatively high anti-reflective property,the light utilization rate of the photovoltaic cell can be increased andthe light conversion efficiency of the photovoltaic cell can beimproved.

In some embodiments of the present disclosure, the aluminum oxide layer17 is provided on the rear surface of the photovoltaic cell. Since thegrowth and annealing temperature of the aluminum oxide layer 17 isrelatively low, octahedral structures of aluminum atoms in the aluminumoxide layer 17 will be transformed into tetrahedral structures after ahigh temperature heat treatment to generate interstitial oxygen atoms.The interstitial oxygen atoms capture valence electrons in the substrate10 to form fixed negative charges, so that the aluminum oxide layer 17shows an electronegativity and an interface electric field directed tothe inside of the substrate 10 is generated at the interface, thuscausing carriers to escape from the interface quickly, reducing aninterface recombination rate and increasing a minority carrier lifetimeof the substrate 10. The PPW layer 18 disposed on the aluminum oxidelayer 17 may effectively prevent subsequent products of sodium ions, ˜OHand ˜CH3 groups from migrating into the photovoltaic cell, block themovement and migration of mobile ions under an external electric field,temperature and humidity, and reduce the potential difference betweenlayers and enhance the anti-PID effect, thus having better anti-PIDperformance and anti-aging/attenuation performance. The silicon nitridelayer 19 disposed on the PPW layer 18 achieves the optimalanti-reflection effect by combining optical path matching, and protectsthe adjacent aluminum oxide layer 17 and polarization phenomenonweakening layer 18 from corrosion caused by the excessive paste. Afterannealing, an H passivation effect of the silicon nitride layer 19 issignificant, which further improves the minority carrier lifetime of asilicon wafer and also prevents subsequent products of Na+, ˜OH and ˜CH3groups from migrating into the photovoltaic cell to a certain extent,thus avoiding power attenuation caused by electric leakage of cellcomponents. The combination of the aluminum oxide layer 17 and thepolarization phenomenon weakening layer 18 reduces the power loss of thecell components, and improves light attenuation performance,heat-assisted light attenuation performance and anti-PID performance ofthe photovoltaic cell.

In an embodiment, as shown in FIG. 2 , the at least one silicon nitridelayer is provided with three silicon nitride layers, i.e., a firstsilicon nitride layer 191, a second silicon nitride layer 192 and athird silicon nitride layer 193 that are stacked in the direction awayfrom the substrate 10. In this embodiment, a refractive index of thethree and silicon nitride layers is in a range of 1.9 to 2.5. Athickness of the first silicon nitride layer 191 is in a range of 5 nmto 20 nm, a thickness of the second silicon nitride layer 192 is in arange of 20 nm to 40 nm, and a thickness of the third silicon nitridelayer 193 is in a range of 40 nm to 75 nm. A refractive index of thefirst silicon nitride layer 191 is in a range of 2.1 to 2.5, arefractive index of the second silicon nitride layer 192 is in a rangeof 2 to 2.3, and a refractive index of the third silicon nitride layer193 is in a range of 1.9 to 2.1. It should be noted that although thereare the same values in the refractive index ranges of every two siliconnitride layers in the above three silicon nitride layers, the refractiveindexes of the three silicon nitride layers need to satisfy thecondition that “the refractive indexes of the plurality of siliconnitride layers decrease layer by layer in the direction away from thesubstrate 10” in practical applications. Therefore, a situation thatevery two silicon nitride layers in the three silicon nitride layershave the same refractive indexes may not happen.

In an embodiment, as shown in FIG. 3 , the at least one silicon nitridelayer is provided with two silicon nitride layers, i.e., a first siliconnitride layer 191 and a second silicon nitride layer 192 that arestacked in the direction away from the substrate 10. In this embodiment,a refractive index of the two silicon nitride layers is in a range of1.9 to 2.5. A thickness of the first silicon nitride layer 191 is in arange of 15 nm to 40 nm, and a thickness of the second silicon nitridelayer 192 is in a range of 35 nm to 110 nm. A refractive index of thefirst silicon nitride layer 191 is in a range of 2.3 to 2.5, and arefractive index of the second silicon nitride layer 192 is in a rangeof 1.9 to 2.2.

Some embodiments of the present disclosure provide a photovoltaicmodule, which includes at least one photovoltaic cell string. Thephotovoltaic cell string is composed of the above photovoltaic cellselectrically connected, for example, the photovoltaic cells illustratedin FIGS. 1 to 3 . The photovoltaic cells are electrically connected inseries and/or parallel in the photovoltaic cell string. The photovoltaicmodule includes, but is not limited to, a laminate module, adouble-sided module, a multi-main grid module, etc. For example, thephotovoltaic cells (e.g., FIG. 1 ) described above can be obtained, andthe cells can be electrically connected with adjacent ones viaconductive materials to form the cell string. A back plate, anethylene-vinyl acetate (EVA) copolymer and the cell string are stackedin a certain order through a lamination process. Then the stackedstructure is installed with a frame to form the photovoltaic module. Thephotovoltaic cells may convert absorbed light energy into electricenergy. The module may transfer the electric energy obtained by thecells to a load.

Some embodiments of the present disclosure provide a method formanufacturing the photovoltaic cell described in the above embodiments.A schematic flow chart of the method for manufacturing the photovoltaiccell is shown in FIG. 4 , which includes the following steps.

In step 101, a substrate is provided.

Specifically, the substrate includes an intrinsic silicon substrate andan emitter. The intrinsic silicon substrate and the emitter form a PNjunction of the photovoltaic cell. As shown in FIGS. 1 to 3 , thesubstrate 10 includes an intrinsic silicon substrate 11 and an emitter12. The intrinsic silicon substrate 11 and the emitter 12 form a PNjunction. For example, the intrinsic silicon substrate 11 may be aP-type substrate, the emitter 12 may be an N-type doped layer, that is,the P-type substrate and the N-type doped layer form a PN junction. Insome embodiments, the intrinsic silicon substrate 11 includes, but isnot limited to, a monocrystalline silicon substrate, a polycrystallinesilicon substrate, a monocrystalline silicon-like substrate, etc. Itshould be noted that a front surface of the substrate 10 is designatedas a light-receiving surface, and a rear surface of the substrate 10refers to a surface opposite to the front surface. In some embodiments,a surface close to the emitter 12 is referred to as the front surface,and a surface close to the intrinsic silicon substrate 11 is referred toas the rear surface.

In step 102, a first passivation layer, a first anti-reflection layerand a first electrode are sequentially disposed on a front surface ofthe substrate in a direction away from the substrate.

As shown in FIGS. 1 to 3 , a first passivation layer 13 and a firstanti-reflection layer 14 are sequentially stacked on the front surfaceof the substrate 10 in the direction away from the substrate 10. Herein,the first passivation layer 13 includes, but is not limited to, analuminum oxide layer, a silicon nitride layer, a silicon oxynitridelayer, etc. The first passivation layer 13 is used to reduce therecombination of carriers, thereby increasing an open circuit voltageand a short circuit current of the photovoltaic cell. The firstanti-reflection layer 14 may be provided with a layer similar to orsubstantially the same as the passivation layer 13, for example,including but not limited to, the aluminum oxide layer, the siliconnitride layer, the silicon oxynitride layer, etc. The firstanti-reflection layer 14 may not only reduce the reflectivity of lightsincident on a surface of the photovoltaic cell, but also passivate thesurface of the photovoltaic cell.

The first passivation layer 13 or the first anti-reflection layer 14 maybe formed by, including but not limited to, plasma enhanced chemicalvapor deposition (PECVD), atomic layer deposition (ALD), chemical vapordeposition (CVD), physical vapour deposition (PVD), etc.

In an embodiment, a first electrode 15 is further formed on the frontsurface of the substrate 10. The first electrode 15 penetrates throughthe first passivation layer 13 and the first anti-reflection layer 14,and forms an ohmic contact with the emitter 12 of the substrate 10. Thefirst electrode 15 may be formed by a metallization process, forexample, by screen printing the conductive paste.

In step 103, a second passivation layer is formed on a rear surface ofthe substrate in the direction away from the substrate.

As shown in FIGS. 1 to 3 , a second passivation layer 20 is formed onthe rear surface of the substrate 10. The second passivation layer 20includes at least one aluminum oxide layer Al_(x)O_(y), where0.8<y/x<1.6. Particularly, 0.8<y/x≤1, 1<y/x<1.5 or 1.5≤y/x<1.6. When theat least one aluminum oxide layer is provided with a single layer (i.e.,an aluminum oxide layer 17), a thickness of the aluminum oxide layer 17is in a range of 4 nm to 20 nm. Particularly, the thickness of thealuminum oxide layer 17 is 5 nm, 10 nm, 15 nm or 20 nm. When forming thealuminum oxide layer 17 with a particular thickness, a ratio of y and xin the aluminum oxide layer 17 is controlled in a range of 0.8 to 1.6,and a refractive index of the aluminum oxide layer 17 is in a range of1.4 to 1.6. Particularly, the refractive index of the aluminum oxidelayer 17 is in a range of 1.55 to 1.59. It should be noted that when theat least one aluminum oxide layer is provided with a plurality of layers(not shown), the refractive index mentioned here should be a refractiveindex of all the aluminum oxide layers, that is, the refractive index ofall of the plurality of aluminum oxide layers is in a range of 1.4 to1.6. Particularly, the refractive index of all of the plurality ofaluminum oxide layers is in a range of 1.55 to 1.59.

In an embodiment, the aluminum oxide layer 17 in the second passivationlayer 20 is prepared by the PECVD. Argon, trimethylaluminium and nitrousoxide may be used as precursors of the aluminum oxide layer 17. Herein,a gas flow ratio of the argon, the trimethylaluminium and the nitrousoxide is in a range of 1:1:1 to 1.5:1:2. Particularly, the gas flowratio is in a range of 1:1:1 to 1:1:2, and the pressure in a PECVDreaction chamber is 0.13 mbar. A thickness of the aluminum oxide layer17 is in a range of 4 nm to 20 nm. A ratio of y and x in the aluminumoxide layer 17 may be controlled in a range of 0.8 to 1.6. A refractiveindex of the aluminum oxide layer 17 is in a range of 1.4 to 1.6.

In an embodiment, the second passivation layer 20 further includes asilicon oxide layer 16. The silicon oxide layer 16 is disposed betweenthe substrate 10 and the aluminum oxide layer 17. The silicon oxidelayer 16 is formed between the substrate 10 and the aluminum oxide layer17 to isolate the aluminum oxide layer 17 from the substrate 10. Thesilicon oxide layer 16 is formed by applying an ozone (O₃) process in aprocess of etching the substrate 10. The dense silicon oxide layer 16 ischemically stable, which may chemically passivate a dangling bond on thesurface of the substrate 10. A thickness of the silicon oxide layer 16is in a range of 0.1 nm to 5 nm. Particularly, the thickness of thesilicon oxide layer 16 is 2 nm, 3 nm or 4 nm.

In step 104, a polarization phenomenon weakening (PPW) layer is formedon a surface of the second passivation layer away from the substrate.

The PPW layer may be configured as an intermediate layer to reduce apotential difference between its upper and lower layers, thus improvingthe anti-PID performance of the photovoltaic cell and further ensuringthe high conversion efficiency of the photovoltaic cell. In someembodiments, as shown in FIGS. 1 to 3 , the PPW layer 18 includes atleast one silicon oxynitride layer Si_(r)O_(s)N_(t), where r>s>t. Aconcentration of silicon atoms in the at least one silicon oxynitridelayer is in a range of 5×10²¹/cm³ to 2.5×10²²/cm³.

In an embodiment, when depositing the at least one silicon oxynitridelayer on the surface of the aluminum oxide layer 17, silanes, ammoniaand nitrous oxide are simultaneously introduced into a reaction chamber,where a gas flow ratio of the silanes, the ammonia and the nitrous oxideis in a range of 1:1:3 to 1:4:6, and the pressure in the reactionchamber is 0.25 mbar. A thickness of the at least one silicon oxynitridelayer is in a range of 1 nm to 30 nm, and a refractive index of the atleast one silicon oxynitride layer is in a range of 1.5 to 1.8. Itshould be noted that when the at least one silicon oxynitride layer isprovided with a plurality of layers, the refractive index mentioned hereshould be a refractive index of all the silicon oxynitride layers, thatis, the refractive index of all of the plurality of silicon oxynitridelayers is in a range of 1.5 to 1.8.

In an embodiment, an intermediate silicon oxide layer is deposited onthe surface of the aluminum oxide layer 17, and precursors of theintermediate silicon oxide layer are the silanes and the nitrous oxide,where a gas flow ratio of the silanes and the nitrous oxide is in arange of 1:3 to 1:6, and the pressure in the reaction chamber is 0.25mbar. After the intermediate silicon oxide layer is formed, nitrogensource gas is introduced to produce nitrogen plasmas to react with theintermediate silicon oxide layer, so as to form the at least one siliconoxynitride layer. That is to say, an intermediate silicon dioxide layeris formed first by the reaction on the surface of the aluminum oxidelayer 17, and then the nitrogen source gas is introduced to producenitrogen plasmas to react with the silicon dioxide layer, so as to formthe at least one silicon oxynitride layer. A thickness of the at leastone silicon oxynitride layer is in a range of 1 nm to 30 nm, and therefractive index of the at least one silicon oxynitride layer is in arange of 1.5 to 1.8.

In step 105, at least one silicon nitride layer is formed on a surfaceof the polarization phenomenon weakening layer away from the substrate.

As shown in FIG. 1 , the at least one silicon nitride layer Si_(u)N_(v)is provided with a single layer (i.e., the silicon nitride layer 19),where 1<u/v<4, and the silicon nitride layer 19 is formed on the surfaceof the PPW layer 18. A thickness of the silicon nitride layer 19 is in arange of 50 nm to 100 nm.

In an embodiment, the silicon nitride layer 19 is prepared by the PECVD,the silanes and the ammonia may be used as precursors of the siliconnitride layer 19. The pressure in the reaction chamber is 0.25 mbar, anda gas flow ratio of the silanes and the ammonia is in a range of 1:1.3to 1:4. A thickness of the silicon nitride layer 19 is in a range of 50nm to 100 nm, and a refractive index of the silicon nitride layer 19 isin a range of 1.9 to 2.5. Particularly, the thickness of the siliconnitride layer 19 is 60 nm, 75 nm or 90 nm.

In an embodiment, the at least one silicon nitride layer is providedwith a plurality of silicon nitride layers. Particularly, the at leastone silicon nitride layer is provided with 2 to 5 silicon nitridelayers, such as 2 layers, 3 layers, etc. As shown in FIG. 2 , the atleast one silicon nitride layer includes a first silicon nitride layer191, a second silicon nitride layer 192 and a third silicon nitridelayer 193. Specifically, precursors of the three silicon nitride layersare introduced into a first reaction chamber of a PECVD equipment, andthe precursors are the silanes and the ammonia. A gas flow ratio of thesilanes and the ammonia is in a range of 1:1.3 to 1:1.5, the pressure inthe first reaction chamber is 0.25 mbar, and the first silicon nitridelayer 191 is formed by the PECVD process. The same kind of precursorsare continuously introduced into the first reaction chamber, a gas flowratio of the silanes and the ammonia is in a range of 1:1.5 to 1:2.2,the pressure in the first reaction chamber is 0.25 mbar, and the secondsilicon nitride layer 192 is formed by the PECVD process. The same kindof precursors are introduced into a second reaction chamber of the PECVDequipment, a gas flow ratio of the silanes and the ammonia is in a rangeof 1:2.2 to 1:4, the pressure in the reaction chamber is 0.25 mbar, andthe third silicon nitride layer 193 is formed by the PECVD process.

Based on the preparation processes, a thickness of the first siliconnitride layer 191 is in a range of 5 nm to 20 nm, a thickness of thesecond silicon nitride layer 192 is in a range of 20 nm to 40 nm, and athickness of the third silicon nitride layer 193 is in a range of 40 nmto 75 nm. A refractive index of the first silicon nitride layer 191 isin a range of 2.1 to 2.5, a refractive index of the second siliconnitride layer 192 is in a range of 2 to 2.3, and a refractive index ofthe third silicon nitride layer 193 is in a range of 1.9 to 2.1. Arefractive index of the three silicon nitride layers is in a range of1.9 to 2.5. It should be noted that although there are the same valuesin the refractive index ranges of every two silicon nitride layers inthe above three silicon nitride layers, the refractive indexes of thethree silicon nitride layers need to satisfy the condition that “therefractive indexes of the plurality of silicon nitride layers decreaselayer by layer in the direction away from the substrate 10” in practicalapplications. Therefore, a situation that every two silicon nitridelayers in the three silicon nitride layers have the same refractiveindexes may not happen.

In an embodiment, as shown in FIG. 3 , the at least one silicon nitridelayer is provided with two silicon nitride layers, i.e., a first siliconnitride layer 191 and a second silicon nitride layer 192. Specifically,precursors of the two silicon nitride layers are introduced into a firstreaction chamber of a PECVD equipment, and the reactants are the silanesand the ammonia. A gas flow ratio of the silanes and the ammonia is1:1.9, a reaction chamber pressure is 0.25 mbar, and the first siliconnitride layer 191 is formed by the PECVD process. The same kind ofprecursors are continuously introduced into the first reaction chamber,a gas flow ratio of the silanes and the ammonia is 1:2.8, a reactionchamber pressure is 0.25 mbar, and the second silicon nitride layer 192is formed by the PECVD process.

Based on the above preparation processes, a thickness of the firstsilicon nitride layer 191 is in a range of 15 nm to 40 nm, and athickness of the second silicon nitride layer 192 is in a range of 35 nmto 110 nm. A refractive index of the first silicon nitride layer 191 isin a range of 2.3 to 2.5, and a refractive index of the second siliconnitride layer 192 is in a range of 1.9 to 2.2.

In step 106, a conductive paste is printed on the surface of the atleast one silicon nitride layer and sintered to form a second electrode.The second electrode penetrates through the second passivation layer,the PPW layer and the at least one silicon nitride layer, and forms anohmic contact with the substrate.

In order to achieve a photovoltaic cell with high anti-PID effect andhigh efficiency, for example, the thicknesses of the second passivationlayer 20, the PPW layer 18 and the silicon nitride layer 19 on the rearsurface of the photovoltaic cell and their corresponding refractiveindexes are designed to be matched. A relationship of the atom number ofeach kind of atoms in the aluminum oxide layer 17 included in the secondpassivation layer 20, the PPW layer 18 and the silicon nitride layer 19is specified through a proper process, so that the refractive index ofall the layers on the rear surface of the photovoltaic cell is within areasonable refractive index range. When the refractive index of all thelayers on the rear surface of the photovoltaic cell is within thereasonable refractive index range and each layer has a suitablethickness, which result in a relatively high anti-reflective property,the light utilization rate of the photovoltaic cell can be increased andthe light conversion efficiency of the photovoltaic cell can beimproved.

In some embodiments of the present disclosure, the aluminum oxide layer17 is provided on the rear surface of the photovoltaic cell. Since thegrowth and annealing temperature of the aluminum oxide layer 17 isrelatively low, octahedral structures of aluminum atoms in the aluminumoxide layer 17 will be transformed into tetrahedral structures after ahigh temperature heat treatment to generate interstitial oxygen atoms.The interstitial oxygen atoms capture valence electrons in the substrate10 to form fixed negative charges, so that the aluminum oxide layer 17shows an electronegativity and an interface electric field directed tothe inside of the substrate 10 is generated at the interface, thuscausing carriers to escape from the interface quickly, reducing aninterface recombination rate and increasing a minority carrier lifetimeof the substrate 10. The PPW layer 18 disposed on the aluminum oxidelayer 17 may effectively prevent subsequent products of sodium ions, ˜OHand ˜CH3 groups from migrating into the photovoltaic cell, block themovement and migration of mobile ions under an external electric field,temperature and humidity, and reduce the potential difference betweenlayers and enhance the anti-PID effect, thus having better anti-PIDperformance and anti-aging/attenuation performance. The silicon nitridelayer 19 disposed on the PPW layer 18 achieves the optimalanti-reflection effect by combining optical path matching, and protectsthe adjacent aluminum oxide layer 17 and polarization phenomenonweakening layer 18 from corrosion caused by the excessive paste. Afterannealing, an H passivation effect of the silicon nitride layer 19 issignificant, which further improves the minority carrier lifetime of asilicon wafer and also prevents subsequent products of Na+, ˜OH and ˜CH3groups from migrating into the photovoltaic cell to a certain extent,thus avoiding power attenuation caused by electric leakage of cellcomponents. The combination of the aluminum oxide layer 17 and thepolarization phenomenon weakening layer 18 reduces the power loss of thecell components, and improves light attenuation performance,heat-assisted light attenuation performance and anti-PID performance ofthe photovoltaic cell.

Comparative Example

A comparative example provides a back structure of a PERC cell. Thespecific structure is shown in FIG. 5 , which includes: a substrate 10having a PN junction; a first passivation layer 13, a firstanti-reflection layer 14 and a first electrode 15 that are sequentiallydisposed on a front surface of the substrate 10 in a direction away fromthe substrate 10; a second passivation layer 20, a silicon nitride layer19 Si_(u)N_(v) and a second electrode 21 that are sequentially disposedon a rear surface of the substrate 10 in a direction away from thesubstrate 10, where 1<u/v<4. The second passivation layer 20 includes atleast one aluminum oxide layer Al_(x)O_(y) (shown as an aluminum oxidelayer 17 in FIG. 5 when provided with a single layer), where0.8<y/x<1.6. A refractive index of the at least one aluminum oxide layeris in a range of 1.4 to 1.6, and a thickness of the at least onealuminum oxide layer is in a range of 4 nm to 20 nm. A refractive indexof the silicon nitride layer 19 is in a range of 1.9 to 2.5, and athickness of the silicon nitride layer 19 is in a range of 50 nm to 100nm. The second passivation layer 20 further includes a silicon oxidelayer 16. The silicon oxide layer 16 is disposed between the substrate10 and the aluminum oxide layer 17 to isolate the aluminum oxide layer17 from the substrate 10, which may avoid a direct contact between thealuminum oxide layer 17 and the substrate 10.

Compared with the photovoltaic cell in the present disclosure shown inFIG. 1 , the difference is that the back structure of the comparativeexample does not have the PPW layer 18, and other structures andpreparation method are the same. Through a comparative experiment, theresults are shown in the following table.

Conversion Open circuit Short circuit Parallel efficiency voltagecurrent resistance Parameter Ncell/% Uoc/mV Isc/A Rs/mΩ WithSi_(r)O_(s)N_(t) 22.897 688.2 10.761 0.988 Without Si_(r)O_(s)N_(t)22.779 685.6 10.752 0.955 Minority Minority carrier carrier lifetimelifetime Fill factor Thickness (before (after Parameter FF/% of layersintering) sintering) With Si_(r)O_(s)N_(t) 82.677 97 128.71 204.93Without Si_(r)O_(s)N_(t) 82.626 84.8 93.91 168.3

Herein, the conversion efficiency of the photovoltaic cell=(open circuitvoltage*short circuit current*fill factor)/(cell area*illuminationamplitude)*100%. It can be seen that the open circuit voltage, the shortcircuit current and the fill factor are proportional to the conversionefficiency. The longer the minority carrier lifetime, the higher theconversion efficiency. It can be seen from the data in the table that aconversion efficiency of a photovoltaic cell with the Si_(r)O_(s)N_(t)on the rear surface is 0.118% higher than that of a photovoltaic cellwithout the Si_(r)O_(s)N_(t) on the rear surface.

The steps in the above methods only aim to make the description clearer.In implementation, the steps may be combined into one or one step may bedivided into multiple sub-steps, which, as long as the same logicalrelationship is included, all fall into the protection scope of thepresent disclosure. Such a trivial amendment or design added to analgorithm or procedure as not changing the algorithm or a core design ofthe procedure falls into the protection scope of the disclosure.

It is not difficult to find that this embodiment is a method embodimentrelated to the first embodiment, and this embodiment may be implementedin cooperation with the first embodiment. The relevant technical detailsmentioned in the first embodiment are still valid in this embodiment,thus not repeated herein in order to reduce repetition. Accordingly, therelevant technical details mentioned in this embodiment may also beapplied in the first embodiment.

Those skilled in the art should appreciate that the aforementionedembodiments are specific embodiments for implementing the presentdisclosure. In practice, however, various changes may be made in theforms and details of the specific embodiments without departing from thespirit and scope of the present disclosure.

What is claimed is:
 1. A photovoltaic cell, comprising: a siliconsubstrate; a first passivation layer disposed on a front surface of thesilicon substrate; and a second passivation layer, a polarizationphenomenon weakening (PPW) layer and at least one silicon nitride layerSi_(u)N_(v) that are sequentially disposed on a rear surface of thesilicon substrate in a direction away from the silicon substrate,wherein 1<u/v<4; wherein the second passivation layer includes at leastone aluminum oxide layer Al_(x)O_(y), wherein 0.8<y/x<1.6, and athickness of the at least one aluminum oxide layer is in a range of 4 nmto 20 nm; wherein the PPW layer includes at least one silicon oxynitridelayer Si_(r)O_(s)N_(t), wherein r>s>t, and a thickness of the at leastone silicon oxynitride layer is in a range of 1 nm to 30 nm; wherein athickness of the at least one silicon nitride layer is in a range of 50nm to 100 nm; and wherein a concentration of silicon atoms in the atleast one silicon oxynitride layer is between 5×10²¹/cm³ and2.5×10²²/cm³.
 2. The photovoltaic cell according to claim 1, wherein theat least one silicon nitride layer includes a first silicon nitridelayer, a second silicon nitride layer and a third silicon nitride layerstacked in the direction away from the silicon substrate, wherein athickness of the first silicon nitride layer is in a range of 5 nm to 20nm, a thickness of the second silicon nitride layer is in a range of 20nm to 40 nm, and a thickness of the third silicon nitride layer is in arange of 40 nm to 75 nm.
 3. The photovoltaic cell according to claim 2,wherein refractive indexes of the first silicon nitride layer, thesecond silicon nitride layer and the third silicon nitride layerdecrease layer by layer in the direction away from the siliconsubstrate.
 4. The photovoltaic cell according to claim 1, wherein thesecond passivation layer further includes a silicon oxide layer, and thesilicon oxide layer is disposed between the silicon substrate and the atleast one aluminum oxide layer.
 5. The photovoltaic cell according toclaim 4, wherein a thickness of the silicon oxide layer is in a range of0.1 nm to 5 nm.
 6. The photovoltaic cell according to claim 1, whereinthe at least one silicon nitride layer includes a first silicon nitridelayer and a second silicon nitride layer that are stacked in thedirection away from the silicon substrate, wherein a thickness of thefirst silicon nitride layer is in a range of 15 nm to 40 nm, and athickness of the second silicon nitride layer is in a range of 35 nm to110 nm.
 7. The photovoltaic cell according to claim 1, wherein the atleast one aluminum oxide layer includes interstitial oxygen atoms. 8.The photovoltaic cell according to claim 1, wherein the siliconsubstrate includes a P-type intrinsic silicon and an N-type doped layer.9. The photovoltaic cell according to claim 1, wherein a refractiveindex of the at least one silicon nitride layer is in a range of 1.9 to2.5.
 10. A photovoltaic module, comprising at least one photovoltaiccell string, wherein each of the at least one photovoltaic cell stringincludes a plurality of photovoltaic cells electrically connected;wherein each of the plurality of photovoltaic cells comprises: a siliconsubstrate; a first passivation layer disposed on a front surface of thesilicon substrate; and a second passivation layer, a polarizationphenomenon weakening (PPW) layer and at least one silicon nitride layerSi_(u)N_(v) that are sequentially disposed on a rear surface of thesilicon substrate in a direction away from the silicon substrate,wherein 1<u/v<4; wherein the second passivation layer includes at leastone aluminum oxide layer Al_(x)O_(y), wherein 0.8<y/x<1.6, and athickness of the at least one aluminum oxide layer is in a range of 4 nmto 20 nm; wherein the PPW layer includes at least one silicon oxynitridelayer Si_(r)O_(s)N_(t), wherein r>s>t, and a thickness of the at leastone silicon oxynitride layer is in a range of 1 nm to 30 nm; wherein athickness of the at least one silicon nitride layer is in a range of 50nm to 100 nm; and wherein a concentration of silicon atoms in the atleast one silicon oxynitride layer is between 5×10²¹/cm³ and2.5×10²²/cm³.
 11. The photovoltaic module according to claim 10, whereinthe at least one silicon nitride layer includes a first silicon nitridelayer, a second silicon nitride layer and a third silicon nitride layerstacked in the direction away from the silicon substrate, wherein athickness of the first silicon nitride layer is in a range of 5 nm to 20nm, a thickness of the second silicon nitride layer is in a range of 20nm to 40 nm, and a thickness of the third silicon nitride layer is in arange of 40 nm to 75 nm.
 12. The photovoltaic module according to claim11, wherein refractive indexes of the first silicon nitride layer, thesecond silicon nitride layer and the third silicon nitride layerdecrease layer by layer in the direction away from the siliconsubstrate.
 13. The photovoltaic module according to claim 10, whereinthe second passivation layer further includes a silicon oxide layer, andthe silicon oxide layer is disposed between the silicon substrate andthe at least one aluminum oxide layer.
 14. The photovoltaic moduleaccording to claim 13, wherein a thickness of the silicon oxide layer isin a range of 0.1 nm to 5 nm.
 15. The photovoltaic module according toclaim 10, wherein the at least one silicon nitride layer includes afirst silicon nitride layer and a second silicon nitride layer that arestacked in the direction away from the silicon substrate, wherein athickness of the first silicon nitride layer is in a range of 15 nm to40 nm, and a thickness of the second silicon nitride layer is in a rangeof 35 nm to 110 nm.
 16. The photovoltaic module according to claim 10,wherein the at least one aluminum oxide layer includes interstitialoxygen atoms.
 17. The photovoltaic module according to claim 10, whereinthe silicon substrate includes a P-type intrinsic silicon and an N-typedoped layer.
 18. The photovoltaic module according to claim 10, whereina refractive index of the at least one silicon nitride layer is in arange of 1.9 to 2.5.